This unit is an excellent demonstration of how to supplement a textbook, bringing into sharp relief the essential aspects of a mathematical topic. All but one document present original content; the exception is a page linking the content to the examples and practice of a specific textbook. Set theory is studied as part of the middle years program (MYP) of the International Baccalaureate (IBO.org), and is prior learning for its diploma program (DP). It is featured to a lessor extent in the GCSE, IGCSE and A Level syllabi. The concepts are essential preparation for those who will study mathematics at the tertiary level, and for those preparing for international competitions. This resource includes over 20 planning and student handouts developed for a ten lesson sequence (50 minutes per lesson) introducing set theory. The student experience of each lesson is focused around exploring a list of mastery targets that encapsulate the skills and meanings of the mathematical content. The mastery targets colour every aspect of each unit's planning and are explicitly reflected in each activity, from the pre-assessment to the final project. The course materials create multiple opportunities for students to assess their progress towards the skills and understanding encapsulated in the mastery targets. The use of sample pages, rubrics and checklists make explicit the actions needed for success. The unit documents include: - Lesson Plan Sequence - List of Mastery Targets - Pre-Assessments - Key Vocabulary - Two Unit Assessments - Five Activities - Student Project - Project Rubric - Prior Learning - Mindset - Sample Student Page : Graphic Organiser - Sample Student Page: Mastery Targets The mathematical content includes: - Well-Defined Sets - Roster Notation - Set Builder Notation - Set Equality - Cardinality - Finite & Infinite Sets - Number Sets Set Theory (Part 2) Set Operations will focus on subsets, basic set operations and venn diagrams.